Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quantas residências há no condado de Highlands?
 ###Tabelas: CREATE TABLE 2003_team (2003_team_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, Position VARCHAR, School VARCHAR, Hometown VARCHAR, MLB Draft VARCHAR) CREATE TABLE schools (schools_id AUTO_INCREMENT PRIMARY KEY, School VARCHAR, Year Founded VARCHAR, Denomination VARCHAR, Language VARCHAR, Grades VARCHAR, Gender VARCHAR, Private/Public VARCHAR) CREATE TABLE florida_counties_ranked_by_per_capita_income (florida_counties_ranked_by_per_capita_income_id AUTO_INCREMENT PRIMARY KEY, County VARCHAR, Per capita income VARCHAR, Median household income VARCHAR, Median family income VARCHAR, Population INT, Number of households INT) CREATE TABLE singles_titles (singles_titles_id AUTO_INCREMENT PRIMARY KEY, Date VARCHAR, Tournament VARCHAR, Surface VARCHAR, Opponent in the final VARCHAR, Score VARCHAR) CREATE TABLE brazil's_40_busiest_airports_by_passenger_traffic (brazil's_40_busiest_airports_by_passenger_traffic_id AUTO_INCREMENT PRIMARY KEY, Rank INT, Location VARCHAR, Total Passengers INT, Annual change VARCHAR, Capacity INT, Capacity in use VARCHAR)  
SELECT AVG Number of households FROM florida_counties_ranked_by_per_capita_income WHERE County = highlands